serial: efm32: use $vendor,$device scheme for compatible string

Wolfram Sang pointed out that "efm32,$device" is non-standard. So use the
common scheme and prefix device with "efm32-". The old compatible string
is left in place until arch/arm/boot/dts/efm32* is fixed.
Reported-by: Wolfram Sang <wsa@the-dreams.de>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Acked-by: Wolfram Sang <wsa@the-dreams.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/devicetree/bindings/serial/efm32-uart.txt

 * Energymicro efm32 UART
 
 Required properties:
-- compatible : Should be "efm32,uart"
+- compatible : Should be "energymicro,efm32-uart"
 - reg : Address and length of the register set
 - interrupts : Should contain uart interrupt
 
@@ -13,7 +13,7 @@ Optional properties:
 Example:
 
 uart@0x4000c400 {
-	compatible = "efm32,uart";
+	compatible = "energymicro,efm32-uart";
 	reg = <0x4000c400 0x400>;
 	interrupts = <15>;
 	efm32,location = <0>;

drivers/tty/serial/efm32-uart.c

@@ -798,6 +798,9 @@ static int efm32_uart_remove(struct platform_device *pdev)
 
 static const struct of_device_id efm32_uart_dt_ids[] = {
 	{
+		.compatible = "energymicro,efm32-uart",
+	}, {
+		/* doesn't follow the "vendor,device" scheme, don't use */
 		.compatible = "efm32,uart",
 	}, {
 		/* sentinel */